This invention relates to an absorption type refrigerator and, more particularly, to an absorption type refrigerator employing an excellent anti-corrosive absorbing solution, and an absorbing solution therefor.
In general, an absorption type refrigerator comprises an absorber containing therein an aqueous absorbing solution which absorbs a refrigerant to form a diluted absorbing solution and generates absorption heat which is cooled by a cooling means, a regenerator for regenerating the diluted absorbing solution by concentrating the diluted absorbing solution through evaporation of the refrigerant, a condenser for condensing the evaporated refrigerant, and an evaporator for evaporating the condensed refrigerant to cool a liquid such as water through heat exchange. In the regenerator used in such an absorption type refrigerator, as means for heating the refrigerant, there are two combustion gas heaters one of which is a type wherein a combustion gas passes among a bundle of gas heating tubes containing therein the absorbing solution and heats the absorbing solution, and other type, a steam heater wherein a steam heating pipe is disposed in the absorbing solution and heats the absorbing solution. The former type of heater is made of carbon steel in view of cost because the combustion gas has a high temperature so that the heater of gas heating tubes, made of material which is not so high in heat conductivity, such as carbon steel, can be used. The latter type of heater, that is, the steam heating pipe is made of copper or its alloy because steam temperature is not so high, so that high heat-conductivity material is needed.
In many cases, an absorption type refrigerator as mentioned above employs an aqueous lithium bromide solution as an absorbing solution. The lithium bromide solution is very corrosive to structural members of the absorption type refrigerator, particularly, to heater members such as heating tubes used in the regenerator. Therefore, many measures have been taken to prevent the structural members being corroded. A typical example of the measures is addition of LiNO.sub.3 and LiOH into a lithium bromide solution. In the lithium bromide solution including LiNO.sub.3 and LiOH, the concentration of LiNO.sub.3 is about 350-500 ppm. This absorbing solution has a corrosion suppressing effect, but the effect is not sufficient.
U.S. Pat. No. 4,311,024 discloses a lithium bromide absorbing solution, the corrosion suppressing effect of which is improved. The lithium bromide absorbing solution comprises 100-500 ppm of LiNO.sub.3, 50-1000 ppm of BTA (benzotriazole), and LiOH. According to the U.S. patent, as a concentration of LiNO.sub.3 contained in the absorbing solution, 350 ppm is better while a concentration of LiOH is not specified. This absorbing solution is improved on a corrosion suppressing effect to reduce an amount of corrosion (weight loss), and at the same time, the absorbing solution greatly suppresses occurrence of pitting corrosion which was apt to occur hitherto. The pitting corrosion suppression effect decreases as temperature of the absorbing solution rises. Therefore, for structural members subjected to a high temperature and in contact with the lithium bromide absorbing solution, such as the above-mentioned gas heating tubes, it is particularly desired to improve more the pitting corrosion suppression effect of the lithium bromide absorbing solution.